I'm in the process of selling my spouse on a M3. I'm trying to do a fair comparison on the cost of driving 20,000 per year electric vs gas. I have the gas costs nailed down but I can't seem to find a good calculator to figure the electric cost. I know my cost for electric is $ 0.10828 per Kw at my home. Maybe $.30 for supercharger? 95/05 split between home and supercharger. So I guess if she drives reasonable what Kw per mile would be reasonable? We live in CO.